Cantilever, cantilever system, scanning probe microscope, mass sensor apparatus, viscoelasticity measuring instrument, manipulation apparatus, displacement determination method of cantilever, vibration method of cantilever and deformation method of cantilever

Abstract

Provided is a cantilever that is capable of bending and deforming in an active manner by itself. The cantilever includes: a lever portion having a proximal end that is supported by a main body part; and a resistor member that is formed in the cantilever and generates heat when a voltage is applied, to thereby deform the lever portion by thermal expansion due to the heat.

1. A cantilever system comprising:
 a cantilever comprising a lever portion having a proximal end that is supported by a main body part, a probe formed on a distal end portion of the lever portion, and a resistor member formed in the lever portion and that generates heat through application of an oscillating AC voltage to deform the lever portion by thermal expansion due to the heat to oscillate the lever portion and the probe; 
 a voltage applying portion for applying an AC voltage to the resistor member; and 
 a displacement measuring mechanism for measuring a displacement of the lever portion, wherein 
 when the voltage applying portion periodically applies an AC voltage having an amplitude center line that is offset from a voltage center line, the lever portion oscillates at a frequency close to a resonance frequency of the lever portion in one of a positive voltage region and a negative voltage region, and when the voltage applying portion periodically applies an AC voltage having an amplitude center line that is not offset from the voltage center line, the lever portion oscillates at a frequency that is substantially a half of the resonance frequency of the lever portion across a positive voltage region and a negative voltage region. 
 
     
     
       2. A cantilever system according to  claim 1 , wherein the lever portion has a thermal expansion portion formed therein in a vicinity of the resistor member, the thermal expansion portion being made of a material having a thermal expansion coefficient larger than that of the lever portion. 
     
     
       3. A cantilever system according to  claim 2 , wherein the thermal expansion portion is formed on one of both sides of the lever portion. 
     
     
       4. A cantilever system according to  claim 2 , wherein the thermal expansion portion is made of a material comprising an insulating material. 
     
     
       5. A cantilever system according to  claim 1 , wherein the lever portion comprises a self displacement sensing lever. 
     
     
       6. A cantilever system according to  claim 5 , wherein the lever portion comprises a self displacement sensing lever provided with a first strain resistor having a resistance value that changes in accordance with a displacement amount. 
     
     
       7. A cantilever system according to  claim 6 , wherein the
 a displacement measuring mechanism measures the displacement of the lever portion based on a change in value of a current flowing in the first strain resistor. 
 
     
     
       8. A cantilever system according to  claim 7 , wherein the voltage applying portion applies a voltage to the first strain resistor to cause the first strain resistor to generate heat and operate as the resistor member. 
     
     
       9. A cantilever system according to  claim 8 , wherein the displacement measuring mechanism detects a voltage applied to the first strain resistor by the voltage applying portion and a change in resistance value of the first strain resistor due to a current generated by the voltage, and measures a displacement of the lever portion based on the voltage and the change thus detected. 
     
     
       10. A cantilever system according to  claim 7 , wherein:
 the cantilever includes a temperature compensating reference electrode in which a second strain resistor is incorporated; and 
 the displacement measuring mechanism measures a displacement of the lever portion based on a difference in value between currents flowing in the first strain resistor and the second strain resistor. 
 
     
     
       11. A cantilever system according to  claim 10 , wherein the displacement measuring mechanism measures a difference in value between currents flowing in the first strain resistor and the second strain resistor by using a Wheatstone bridge circuit. 
     
     
       12. A cantilever system according to  claim 10 , wherein the displacement measuring mechanism measures a difference in value between currents flowing in the first strain resistor and the second strain resistor by using a differential amplifier circuit. 
     
     
       13. A cantilever displacement measuring method of measuring a displacement of the cantilever of the cantilever system according to  claim 6 , the method comprising:
 applying a voltage to the resistor member; and 
 measuring a displacement of the lever portion based on a change in value of a current flowing in the first strain resistor. 
 
     
     
       14. A cantilever displacement measuring method according to  claim 13 , further comprising applying a voltage to the first strain resistor to cause the first strain resistor to generate heat and operate as the resistor member. 
     
     
       15. A cantilever displacement measuring method according to  claim 14 , further comprising detecting the voltage applied to the first strain resistor and the change of a resistance value of the first strain resistor based on a current generated by the voltage, to thereby measure a displacement of the lever portion. 
     
     
       16. A cantilever displacement measuring method according to  claim 13 , further comprising referring to a temperature compensating reference electrode in which a second strain resistor is incorporated, and measuring a displacement of the lever portion based on a difference in value between currents flowing in the first strain resistor and the second strain resistor. 
     
     
       17. A cantilever displacement measuring method according to  claim 16 , wherein the difference in value between currents flowing in the first strain resistor and the second strain resistor is measured using a Wheatstone bridge circuit. 
     
     
       18. A cantilever displacement measuring method according to  claim 16 , wherein the difference in value between currents flowing in the first strain resistor and the second strain resistor is measured using a differential amplifier circuit. 
     
     
       19. A cantilever system according to  claim 1 , wherein the voltage applying portion includes a square root circuit for computing a square root of a voltage value, and the voltage applying portion converts a voltage signal that is proportional to an amount to be deformed by the square root circuit into a voltage, and applies the voltage to the resistor member. 
     
     
       20. A cantilever system according to  claim 1 , wherein the voltage applying portion increases the voltage to compensate a temperature decrease of the resistor member due to thermal radiation, and applies the increased voltage to the resistor member. 
     
     
       21. A cantilever system according to  claim 1 , wherein the voltage applying portion and the displacement measuring mechanism are operated alternately in a time cycle. 
     
     
       22. A cantilever system according to  claim 21 , wherein the voltage applying portion and the displacement measuring mechanism are operated alternately in a time cycle satisfying the expression below,
     S≦q/f,    
 where S denotes the time cycle, q denotes a Q value, and f denotes the resonance frequency of the cantilever lever portion. 
 
     
     
       23. A scanning probe microscope comprising the cantilever system according to  claim 1 . 
     
     
       24. A cantilever comprising:
 a deformable lever portion having a proximal end portion that is supported in a cantilever manner by a main body part and having a probe formed on a distal end portion thereof; and 
 two resistor members positioned on the lever portion in spaced-apart relation in a widthwise direction of the lever portion and responsive to an applied oscillating voltage to generate heat that deforms the lever portion by localized thermal expansion to effect oscillation of the lever portion and the probe. 
 
     
     
       25. A cantilever according to  claim 24 ; including wiring electrically connected to the two resistor members and terminating in connection terminals for applying alternating voltage to each resistor member. 
     
     
       26. A cantilever according to  claim 25 ; wherein the lever portion has one or more openings in the proximal end portion thereof to facilitate deformation and oscillation of the lever portion, and each resistor member is positioned adjacent the one or more openings. 
     
     
       27. A cantilever according to  claim 24 ; wherein the lever portion has one or more openings in the proximal end portion thereof to facilitate deformation and oscillation of the lever portion, and each resistor member is positioned adjacent the one or more openings. 
     
     
       28. A cantilever according to  claim 24 ; including a thermal expansion portion provided on the lever portion in the vicinity of the resistor members, the thermal expansion portion having a thermal expansion coefficient larger than that of the lever portion. 
     
     
       29. A cantilever according to  claim 28 ; wherein the thermal expansion portion is made of insulating material. 
     
     
       30. A cantilever according to  claim 24 ; including strain resistors positioned on the lever portion, each strain resistor having a resistance value that changes in accordance with displacement of the lever portion. 
     
     
       31. A cantilever according to  claim 30 ; wherein each strain resistor is superposed over a respective resistor member. 
     
     
       32. A cantilever according to  claim 30 ; wherein the lever portion is comprised of plural layers superposed one over another, the resistor members being provided on one layer and the strain resistors being provided on another layer which is insulated from the one layer.